Bovine respiratory syncytial virus infection

Abstract

Bovine respiratory syncytial virus (BRSV) infection is one of the most important respiratory tract diseases in cattle. BRSV is closely related to human respiratory syncytial virus (HRSV), an important cause of lower respiratory tract disease (LRTD) in children. A high degree of genetic and antigenic diversity among BRSV isolates, high mutation rate and tolerance to mutation fixation result in recurrent infections, short term immunity and vaccination ineffectiveness. Based on the variability of sequence coding for glycoprotein G, BRSV has been classified into six different genetic subgroups, while similar analysis of the N and F genes resulted in only five subgroups, illustrating the higher rate of evolution of the G gene. Mutations within conserved parts of glycoprotein G indicate continuous BRSV evolution, enabling virus escape from the host immune system. Longterm bovine vaccination has resulted in the occurrence of new geographically specific virus variants detected in Italy and Croatia. The lack of data on BRSV genetic diversity in many other countries indicates the need for identification of new genetic subgroups in order to develop an effective vaccine.